Multi-agent location system in wireless networks

In this paper we propose a flexible Multi-Agent Architecture together with a methodology for indoor location which allows us to locate any mobile station (MS) such as a Laptop, Smartphone, Tablet or a robotic system in an indoor environment using wireless technology. Our technology is complementary to the GPS location finder as it allows us to locate a mobile system in a specific room on a specific floor using the Wi-Fi networks.The idea is that any MS will have an agent known at a Fuzzy Location Software Agent (FLSA) with a minimum capacity processing at its disposal which collects the power received at different Access Points distributed around the floor and establish its location on a plan of the floor of the building. In order to do so it will have to communicate with the Fuzzy Location Manager Software Agent (FLMSA). The FLMSAs are local agents that form part of the management infrastructure of the Wi-Fi network of the Organization.The FLMSA implements a location estimation methodology divided into three phases (measurement, calibration and estimation) for locating mobile stations (MS). Our solution is a fingerprint-based positioning system that overcomes the problem of the relative effect of doors and walls on signal strength and is independent of the network device manufacturer.In the measurement phase, our system collects received signal strength indicator (RSSI) measurements from multiple access points. In the calibration phase, our system uses these measurements in a normalization process to create a radio map, a database of RSS patterns. Unlike traditional radio map-based methods, our methodology normalizes RSS measurements collected at different locations on a floor. In the third phase, we use Fuzzy Controllers to locate an MS on the plan of the floor of a building.Experimental results demonstrate the accuracy of the proposed method. From these results it is clear that the system is highly likely to be able to locate an MS in a room or adjacent room.     

Interannual vineyard crop variability in the Castilla–La Mancha region during the period 1991–1996 with Landsat Thematic Mapper images

The vineyard crop is considered an indicator of vegetation cover processes in the Castilla–La Mancha region, as the crop has undergone far-reaching changes in the last ten years: abandonment, removal of vineyards and replacement with other crops such as cereal. The so-called ‘Change detection’ is a process that allows identification of differences in the state of the vineyard by observing it at different times. Essentially, it involves the ability to quantify temporal effects using multi-temporal datasets.

The aim of this study is to analyse the vineyard variability during the period 1991–1996 using different Landsat-5 Thematic Mapper (TM) images belonging to an identified period that highlights differences in the vegetation phenology changes. The images were firstly georeferenced and radiometrically normalized for the change detection purpose. The study area is located in central Spain and involves five councils belonging to the Castilla–La Mancha region: Mota del Cuervo, Las Mesas, Tomelloso, Socuellamos and Villarrobledo, with a surface area of 174?040?ha. This area is especially cultivated by the vineyard crop. Moreover, the study area was classified with the images acquired in 1991, using the multi-temporal masking techniques for the vineyard inventory.

The changes experimented by the vineyard have been grouped in three categories: cereal (CE), abandoned vineyard (AB) and bare soil (BS). Therefore, two methods of Normalized Difference Vegetation Index (NDVI) image difference and NDVI Change Vector Analysis (CVA) were used to map these categories of change. The results indicate that 28.4% of vineyard area undergoes changes during the period 1991–1996. The results have been checked with the ground data and all information is highly conformed.     

Multisensor comparison of NDVI for a semi‐arid environment in Spain

The joint use of multiresolution sensors from different satellites offers many opportunities to describe vegetation and its dynamics. This paper introduces the concept of a virtual constellation (defined as an ensemble of all Earth Observation satellites in orbit that satisfy common requirements) for agricultural applications and contributes to providing the necessary inter‐sensor calibration methodology for spectral reflectances and NDVI. For this purpose, we performed an observational study, comparing reflectances and the Normalized Difference Vegetation Index (NDVI), from near‐synchronous image pairs of Landsat 7 Enhanced Thematic Mapper Plus (ETM+), as the reference sensor and Landsat 5 Thematic Mapper (TM), IRS 1C/D LISS‐III (LISS), Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER), QuickBird, and NOAA Advanced Very High‐resolution Radiometer (AVHRR). Linear relationships were found for the intercalibration of reflectances and NDVI from one sensor to another, for all sensors, provided that some spatial aggregation was performed. The main source of data dispersion in our linear cross‐sensor translation equations is the geolocation uncertainty inherent in the process of geometric correction. Consequently, spatial aggregation always needs to be performed if (different or the same) sensors are to be used to derive time‐series of biogeophysical parameters over heterogeneous areas. The homogenous zone approach developed here is recommended as an excellent tool for deriving robust new cross‐sensor relationships, provided that the selected homogeneous crops cover the full NDVI range. The linear cross‐sensor relationships derived from one image pair were shown to be valid for the whole season and for all areas with similar vegetation and climate.     

The environmental paradox in generation: How South America is gradually becoming more dependent on thermal generation

There has been an increasing focus on global warming, emission of green house gases (GHG), and the problems this might create. In this article, we review the trend in sustainable and renewable electricity generation in South America, where the generation portfolio increasingly depends on thermal generation, in particular gas. South America is a region that has relatively low emissions, but the current development is not desirable in environmental terms. We analyze the underlying reasons for this development, which is related to security of supply, deregulation, and the cost of renewable energy. We review and discuss the policies to promote renewables in the region. We analyze the potential advantages and drawbacks of different types of market interventions, such as direct subsidies that create potentially strong market distortions, more sophisticated market interventions that might be less intrusive but not necessarily as effective as, e.g. firm energy markets. We also review market-based solutions such as the Clean Market Mechanism and its potential, and the use of renewable electricity in non-interconnected zones, which might be one of the most economically attractive applications of renewables. However, without a stronger and more aggressive intervention from the governments in the region it is unlikely that the increase in thermal generation can be stopped.     

Dynamics of alternative modes of RNA replication for positive-sense RNA viruses

We propose and study nonlinear mathematical models describing the intracellular time dynamics of viral RNA accumulation for positive-sense single-stranded RNA viruses. Our models consider different replication modes ranging between two extremes represented by the geometric replication (GR) and the linear stamping machine replication (SMR). We first analyse a model that quantitatively reproduced experimental data for the accumulation dynamics of both polarities of turnip mosaic potyvirus RNAs. We identify a non-degenerate transcritical bifurcation governing the extinction of both strands depending on three key parameters: the mode of replication (α), the replication rate (r) and the degradation rate (δ) of viral strands. Our results indicate that the bifurcation associated with α generically takes place when the replication mode is closer to the SMR, thus suggesting that GR may provide viral strands with an increased robustness against degradation. This transcritical bifurcation, which is responsible for the switching from an active to an absorbing regime, suggests a smooth (i.e. second-order), absorbing-state phase transition. Finally, we also analyse a simplified model that only incorporates asymmetry in replication tied to differential replication modes.     

Vegetation cover seasonal changes assessment from TM imagery in a semi-arid landscape

This work evaluates the suitability of spectral mixture analysis (SMA) methods to assess vegetation cover seasonal changes in a desertification context. Our main interest is to produce remotely sensed derived maps, sensitive to vegetation activity and quite independent of the soil background. A further aim is to analyse the inter-annual variations of this magnitude for different natural vegetation species, in response to seasonal and climatic changes. Fractional vegetation cover (FVC) was obtained using a Variable Endmember Spectral Mixture Analysis (VESMA) technique. The aim is to identify the main vegetation cover and lithological units and decompose them in separate stages. The use of specific spectral signatures for each pixel allows for a better adaptation of the endmembers to local conditions, which is an important prerequisite to ensure the accuracy of fractions. The method has been tested on a well documented area, the Guadalentin river basin, located in south-eastern Spain. Unlike pine forest and stipa classes, rosmarinus, sparse shrubs and seasonal grasses classes displayed larger inter-annual variability, showing higher stress in response to water availability. A comparative analysis between FVC and the Normalized Difference Vegetation Index (NDVI) was also conducted. Average values were used as indicators of the dynamics of the vegetation cover, with the variance of each vegetation class giving similar results. The correlation between both magnitudes varied from 55% for the class with least coverage to 90% for the densest vegetation class. Regarding seasonal evolution, the average values and standard deviations of the changes in each vegetation class in specific periods were related to seasonal changes and the effects of the rainfall pattern. Significant differences were found between the two methods, with FVC showing a higher coherence.     

Assessment of potential approaches to improve Eucalyptus globulus kraft pulping yield

The main goal of this work is to study the potential approaches to improve polysaccharides retention during Eucalyptus globulus kraft pulping. The addition of anthraquinone to kraft pulping leads to the highest pulp yield while the addition of urea promotes lower depolymerization of polysaccharides (higher pulp viscosity), but does not have a significant effect on yield. The early interruption of kraft cooking followed by oxygen delignification is a reliable approach to increase pulp yield, particularly when pulping is interrupted at the end of the faster and more selective kinetic regime (bulk phase). Yield loss during oxygen delignification is considerably lower than that incurred in the last phase of kraft pulping. Pulping with OH^?/HS^? charge profiling, carried out with liquor injection in three different phases leads to a yield increase. However, this increase results from a lower total alkali charge applied when profiling pulping is compared to standard pulping conditions, rather than to alkali profiling. Standard kraft pulping with different active alkali (AA) charges demonstrated that this operational variable is determinant for pulp yield and viscosity. Pulping experiences with lower AA (14%) resulted in a higher and almost constant pulp viscosity and in a higher pulp yield, assigned to improved retention of both cellulose and xylan. During the last stage of pulping, cellulose content decreases, this being mainly responsible for the decrease of pulp yield, while xylan content is almost constant, a feature attributed to the peculiar structure of this E. globulus's hemicellulose. Copyright © 2007 Society of Chemical Industry     

Distribution of lipids and trace minerals in different muscle sites of farmed and wild turbot (Psetta maxima)

Lipid and trace mineral composition were studied in different sites of the edible flesh of farmed and wild turbot (Psetta maxima). Lipid matter (total content, sterols, tocopherols) showed to accumulate in the edge zone (EZ), except for phospholipid (PL), which provided a distribution that was found to be independent from the kind of turbot and the zone considered. Fatty acid composition of total lipids showed a non‐homogeneous distribution, as the EZ exhibited a different fatty acid group composition (higher monounsaturated and lower polyunsaturated and ω3/ω6 ratio values) than the other zones considered; fewer differences were observed by considering the PL fatty acid composition. Most minerals (Ca, Cu, Fe, Mn and Se) studied showed to be homogeneously distributed along the muscle sites of the wild fish, while more differences were obtained when considering the farmed one. For both kinds of turbots, the most important difference was obtained in the case of Zn, as a largely higher content in the EZ than in the other zones was detected. A close relationship between Zn and total lipid contents (r² = 0.90 and 0.76 for farmed and wild turbots, respectively) was observed.